Yellowstone Volcano Had Two Super Eruptions That Caused Volcanic Winters

The supervolcano that lies under the Yellowstone National Park is feared to erupt soon. Findings of a new study offer glimpse on what happened when the volcano erupted about 6,300,000 years ago.

Twin Eruptions

Geologist Jim Kennett, from the University of California Santa Barbara, and colleagues suggest that the Yellowstone volcano actually had two powerful eruptions more than 6 million years ago.

The researchers said that the closely spaced volcanic winters occurred at a time when our planet was warming up following an ice age. The twin cooling periods each lasted more than 80 years and stalled climate change.

Super Eruptions Caused Drop In Global Temperature

The twin eruptions, which occurred 170 years apart, sent massive amounts of ash and sulphur dioxide into the atmosphere. The ash and sulfur dioxide in the sky blocked sunlight from reaching the Earth's surface and caused a drop in global temperature, cooling the ocean by about 3 degrees Celsius. The impact of these eruptions is such that our planet experienced two distinct volcanic winters.

In the new study presented at Geological Society of America annual meeting in Seattle, the researchers reported finding two distinct layers of ash that bear the unique chemical footprint of the Yellowstone volcano in the seafloor sediments in Southern California's Santa Barbara Basin. The layers of ash, also known as tephra, are squeezed among sediments that hold the detailed geological record of the ocean and climate change.

Cooling Events And Time Of The Eruptions

Kennett and colleagues also discovered that the onset of the cooling events was abrupt and coincided precisely at the time of these eruptions.

In each of these cooling events, the cooling lasted longer than it should be based on simple climate models. The researchers said that the magnitude and duration of the cooling suggested there are other feedbacks involved, possibly increased sunlight-reflecting sea ice and snow cover, or change in the circulation of the ocean that would cool the Earth for a longer time.

"Volcanic winters of this duration are significantly longer than most models predict based on atmospheric dust and sulfur loads, and suggest involvement of positive climatic feedbacks including oceanographic effects," the researchers wrote in their study. "These cool episodes also suggest that the global climate system was highly sensitive in response to such perturbations during deglacial transitions."

Yellowstone Supervolcano

The Yellowstone volcano can release more than 1,000 cubic kilometers of ash and rock at once, which is equivalent to 2,500 times more than the amount of materials belched out by St. Helens in 1980.